Process of making indigo and intermediate products.



Nrrnn mm FFKCEG FATENT BRUNO RICHARD SEIFERT, OF RADEBEUL,.AND CURTPHILIPP AND MAX HERMANN GMEINER, OF DRESDEN, GERMANY, ASSIGNORS TO CHEM-ISOI-IE FABRIK VON HEYDEN, AOTIENGESELLSCHAFT, OF RADEBEUL,

NEAR DRESDEN, GERMANY.

PROCESS OF MAKING INDIGO AND INTERMEDIATE PRODUCTS.

SPECIFICATION forming part of Letters Patent No. 714,042, dated November18, 1902. Application filed December 21, 1901. Serial No. 86,796.(SpecimensJ To all whom it may concern;

Beit known that we, BRUNO RICHARD SEI- FERT, a resident of Radebeul,near Dresden, and Com: PHILIPP and MAX HERMANN-GMEI- NER, residents ofDresden, Kingdom of Saxony, Germany, subjects of the King of Saxony,have invented a new and usefullmprovement in Processes of Making Indigoand Intermediate Products, of Which the following is a specification.

Vorlaender and Weissbrenner (Bem'chte der Deutschen O'hemischenGesellschaft 33, page 556) have observed that the acetylphenylglycin-o-carboxylic acid diethyl ester 0H,0oo0,n,

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is transformed into indoxyl and indigo by the action of twenty per cent.boiling potash-lye. The Badische Anilin und Soda Fabrik has carried theresearch in this direction further and extended this reaction to theneutral esters of phenyl-glycin-o-carboxylic acid, which are substitutedin the nitrogen by an organic acid residue. (French Patent No. 295,814.)We have now discovered that these expensive organic acid residues can bereplaced with good results by a very cheap inorganic acidresidue-namely, the nitroso group. These hitherto unknown alkyl estersof nitroso-phenylglycin-o-carboxylic acid are obtained in quantitativeyield. by the action of nitrosifying agents upon the dialkyl esters. Forexample, two hundred and fifty-one part-s phenyl-glycino-carboxylic aciddiethyl ester are dissolved in one thousand parts glacial acetic acidand into the mixture, cooled to 0 centigrade, there is allowed to run,while well stirring, a solution of seventy to seventy-two parts sodiumnitrite in two hundred parts water. The mixture is then poured ontoice-water, when the nitroso diester separates out as heavy dark-red oil.The nitrosification of the dialkyl esters can naturally also be effectedaccording to the other usual methods of nitrosifying. In the same Waynitrosified dialkyl esters of phenyl-glycin-ortho-carboxylic acids, inwhich nucleus hydrogen is substituted by substitutes, are obtained bynitrosifying the dialkyl esters of those substituted acids. Thesenitrosified dialkyl esters are oily bodies of the constitution 00o alkylThey are transformed with striking ease into indoxyl derivatives andindigo on treatment with solutions having an alkaline reaction. Example1: One part nitroso-phenyl-glycino-carboxylic acid diethyl ester isheated to boiling, with ten parts twenty-per-cent. potash-lye, using areflux condenser and care being taken to exclude the air asfar aspossible. After the ester is completely dissolved the contents of theboiler are cooled and air is led through them, when the indigocoloringmatter separates out. Indigo coloring-matters substituted in thenucleus are obtained by the employment of nitrosifiedphenylglycin-o-carboxylic acid esters substituted in the nucleus. Thetreatment of the nitroso esters may with advantage be carried out withagents having an alkaline reaction in the presence of reducing agents.Thus substances having an alkaline and reducing actionfor example,alkaline sulfids-are particularly suitable for the purpose.

Example 11: One hundred parts,by Weight, of thenitrosophenyl-glycin-o-carboxy1ic acid diethyl ester are mixed into ninehundred parts of a ten-per-cent. aqueous solution of sodium sulfid andwhile being well stirred are heated on the Water-bath until a prettybrisk reaction begins. After the completion of same one hundred andeighty parts of a thirty-four-per-cent. soda-lye are allowed to run inand the mixture is heated for several hours on the water-bath until theformation of the indigo leuco compound or vat is completed. Dilution isthen made with one indigo leuco compound or vat.

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thousand parts water, and the indigo is precipitated by leading in acurrent of air. The indigo is filtered off, washed, and dried.

Instead of first treating with alkali sulfid and then with soda-lyealkali sulfid can be used alone, and in general substances which have asimultaneous alkaline and reducing action can be used.

The formation of the indigo coloring-matters from the nitroso esters, ashereinbefore described, takes place in two or three phases of reaction,which, if desired, can be kept separate. In the first phase the nitrosoesters are transformed into ammonia insoluble intermediate products,most likely pseudo-indoxylic acid esters which in the second phase aretransformed by the further treatment with alkaline agents into indoxylicacid esters which are soluble in ammonia and which in the third phaseare transformed by the further treatment with alkali into indoxyl orThis third phase is already known in literature. If it is desired tostop the reaction at the end of the first phase, the procedure may be,for example, as follows:

ExampleIII: Two hundred and eighty parts, by weight, ofnitroso-phenyl-glycino-carbox ylic acid diethyl ester are dissolved inone thousand parts of alcohol, two hundred and fifty parts,by weight,ofa thirty-per-cent. ammonia are added and sixty-eight to seventy partsof sulfureted hydrogen are introduced while well cooled. After standingfor several days at the ordinary temperature the precipitated sulfur isfiltered off and the alcohol is completely distilled off. The residue istreated with diluted aqueous ammonia for separating out the indoxyl acidester formed and finally recrystallized from alcohol with the aid ofbone-black. In this way yellowgreen crystals of fusing-point 183centigrade are obtained. These are insoluble in water and alkalies,hardly soluble in alcohol, more readily soluble in glacial acetic acid.According to its action and to analysis the compound seems to be thepseudo-indoxylic acid ester isomeric to the indoxylic acid ester solublein alkali, which pseudo ester is of the constitution 00 0 11/ OGOOC2H5.

This compound is in further treating it with substances acting in analkaline manner transformed without difiiculty into the normal alkalisoluble indoxylic acid ester. (By treating with acids the compoundremains essentially unchanged.) If it is desired to stop the reaction atthe end of the second phase, the procedure may be, for example, asfollows:

Example IV: One hundred parts nitrosophenyl-glycin-o-carboxylic aciddiethyl ester are stirred into six hundred parts of a twentyper-cent.soda-lye at ordinary temperature.

After a short time the separation of crystals of the. sodium compound ofthe indoxylic acid ethyl ester begins, and after twelve to fourteenhours the reaction mass sets to a thick paste. This is siphoned or drawn0E, dissolved in water, and acidified. The compound thus precipitatedshows itself to be identical in all respects with the indoxylic acidethyl ester first prepared by A. Von Baeyer.

Instead of using agents having only an al kaline reaction for the firstphase agents having an alkaline and reducing action can also be usedwith advantage.

Example V: One hundred parts nitrosophenyl-glycin-o-carboxylic aciddiethyl ester are heated on the water-bath with a solution of seventyparts of sodium sulfid in one thousand parts water until a prettyviolent reaction commences, being well stirred during heating. After thetermination of the reaction the mixture is allowed to cool,supersaturated with dilute acid, and filtered. From the residue offiltration the indoxylic acid ester can be extracted by the usualextracting mediafor example, alcohol, ether, &c.

The indoxylic acid esters, as is already known in literature, aretransformed into in digo by further heating with alkali and oxidation ofthe resulting leuco compound or vat by air or other oxidizing agents.

We claim- 1 The herein-described improvement in the process of producingindigo coloring-matters consisting in transforming the dialkyl esters ofnucleus-substituted and non-substi tuted phenyl-glycin-o-carboxylicacids into the products nitrosified in the nitrogen, treating the samewith agents having an alkaline reaction and oxidizing the leuco compoundor vat thus obtained.

2. The herein-described improvement in the process of producing indigocoloring-matters consisting in transforming the dialkyl esters ofnucleus-substituted and non-substituted phenyl-glycin-o-carboxylic acidsinto the products nitrosified in the nitrogen, treating the same withagents having an alkaline and reducing action and oxidizing the leucocompound or vat thus obtained.

3. The herein-described improvement in the process of producing indigocoloring-mat ters consisting in transforming the dialkyl esters ofnucleus-substituted and non-substi-' tuted phenyl-glycin-o-carboxylicacids into the products nitrosified in the nitrogen by treating theseesters with nitrosifying agents, convertingthesenitrosified estersintopseudoindoxylic acid esters, transforming the latter into indoxylic acidesters and transforming; those indoxylic acid esters into indigocoloring-matters by further action of alkalies and oxidation.

4. Theherein-described method of producing the intermediate productpseudo-indoxylic ester consisting in treating the nitrosified esters ofphenyl-glycin-o-carboxy1ic acids with agents having an alkaline action.

5. The herein-described method of producing the intermediate productpseudo-indoxylic ester consisting in treating the nitrosified esters ofphenyl-glycin-o-carboxylic acids with agents having an alkaline action,in the presence of reducing agents.

6. The pseudo-indoxylic acid ester herein described, as a new technicalbody which is a crystalline powder insoluble in water and a1- kalies andcapable of being transformed by alkaline agents into indoxylic acidester.

7. The herein-described method of producing the intermediate productindoxylic acid ester consisting in treating the nitrosified esters ofphenyl-glycin-o-carboxylic acids with agents having an alkaline action.

8. The herein-described method of producing the intermediate productindoxylic acid ester consisting in treating the nitrosified esters ofphenyl-glycin-o-carboxylic acids with agents having an alkaline action,in the presence of reducing agents.

In testimony that we claim the foregoing as our invention we have signedour names, in presence of two witnesses, this 9th day of December, 1901.

BRUNO RICHARD SEIFERT. OURT PHILIPP. MAX HERMANN GMEINER.

Witnesses:

HERNANDO DE SoTo, PAUL ARRAS.

